lo Sept., 1910] " Scab " a/id Eel-icorm in Potatoes. 



573 



The following table gives the results from the use of this substance: — 



As seen, a slight increase took place in two plots which, however, is so 

 small as to be negligible, while in the third a decided decrease took place. 

 The sample from plot 5 was in two cases cleaner than that from No. i, 

 and this was no doubt due to the fact that the first named received clean 

 formalin-treated seed, whereas plot i was sown with scabby seed un- 

 treated. Here, again, Mr. Summers' plot fails to agree with the results 

 from the plots in the Ballarat district. 



Spraying. — As spraying is becoming a general practice with potato 

 growers in New Zealand and countries where Irish Blight and other fun- 

 gus diseases are prevalent, it was decided to obtain a spraying machine 

 in order to try the effect of sprays on the general health of the potato crops. 



A Victorian pump, kindly lent by Messrs. Langwill Bros, and Davies, 

 was mounted on a Tasmanian carriage capable of spraying five rows at a 

 time. The power for driving the pump was obtained off the main axle 

 by a clutch and crank connecting with the handle of the pump by an iron 

 rod. This machine was .sent to the various farms, and certain rows of 

 each plot sprayed with Bordeaux mixture and Paris green. In some 

 cases, also, a small area was sprayed for those farmers who were desirous 

 of testmg the machine. 



The .spray used was Bordeaux mixture (bluestone, 6 lbs. ; lime, 4 lbs. ; 

 water, 50 galls.) ; with the addition of Paris green. It was made in the 

 usual way by pouring the dissolved bluestone and lime water slowly to- 

 gether into a third ves.sel and stirring well ; to this was added 4 ozs. of 

 Paris green and the mixture carefully .strained into the barrel on the 

 machine. 



The action of the spray seems to have been to increase the general 

 health of the plant to some extent. After spraying the plants looked 

 fresh and healthy, and as the returns in most cases show, a small increase 

 of yield took place, no doubt owing to the increased vigour of the plant. 

 The beneficial effect of the spray on an under-surface disease Tike Scab 

 seems to be very doubtful, and it is difficult to see how it could affect it 

 unless the disease had its origin at or above the surface of the ground. 

 No doubt spraying would yield much better results where the leaves or 

 stalks of the plant were attacked by disease. 



As will be seen, there was a slight increase of clean potatoes in all the 

 sprayed rows at Mr. Downey's farm, while at Mr. Shearer's a small de- 

 crease took place. Mr. Summers' plots show great variation, the average 

 working out a slight increase. 



One or two of the farmers expressed the opinion that the patches 

 sprayed for them looked cleaner and healthier during the growing period, 

 but that the yield of clean potatoes was about the same as the unsprayed 

 part of the field. 



